Inverter for light source device, light source device, display device and liquid crystal display device

Abstract

In a light source inverter rectifier circuits are respectively connected to a CCFL in a substantially U-shaped lamp and a CCFL in a substantially U-shaped lamp, and the outputs from the rectifier circuits are fed to a stabilization circuit. Thus, the stabilization circuit monitors an average of currents flowing through the substantially U-shaped lamps. This makes it possible to make uniform the currents flowing through the substantially U-shaped lamps.

1. A light source inverter comprising:
 power supply sections that are respectively provided to individual ones of a plurality of light-emitting sections, each of the plurality of light-emitting sections including a plurality of light-emitting cathode fluorescent lamps, each of the power supply sections being arranged to independently apply alternating-current voltages to only a corresponding one of the plurality of light-emitting sections; 
 a control section arranged to control electric power that is applied by the power supply sections to the plurality of light-emitting sections; and 
 a current detection section arranged to detect currents flowing through two separate and independent ones of the plurality of light-emitting sections, to which different power supply sections apply alternating-current voltages, to determine an average of said detected currents, and to generate an output based on said average of said detected currents; wherein 
 the control section controls the electric power applied by the power supply sections to the light-emitting sections based on the currents detected by said output from the current detection section such that the plurality of light-emitting sections are independently controlled on an individual basis. 
 
     
     
       2. The light source inverter of  claim 1 ,
 wherein the current detection section comprises:
 a first half-wave rectifier circuit arranged to detect and half-wave rectify the current flowing through one of the two light-emitting sections; 
 a second half-wave rectifier circuit arranged to detect and half-wave rectify the current flowing through the other of the two light-emitting sections; and 
 a stabilization circuit arranged to combine signals from the first and second half-wave rectifier circuits to determine an average of the currents flowing through the two light-emitting sections, and 
 
 the control section operates based on an output from the stabilization circuit. 
 
     
     
       3. The light source inverter of  claim 1 ,
 wherein the light-emitting sections are each a substantially U-shaped light-emitting section composed of two of the light-emitting cathode fluorescent lamps, and the current detection section detects, in each of the two of the light-emitting sections, a current flowing through one of the two light-emitting cathode fluorescent lamps. 
 
     
     
       4. The light source inverter of  claim 3 ,
 wherein the current detection section comprises:
 a first half-wave rectifier circuit arranged to detect and half-wave rectify the current flowing through one of the two light-emitting sections; 
 a second half-wave rectifier circuit arranged to detect and half-wave rectify the current flowing through the other of the two light-emitting sections; and 
 a stabilization circuit arranged to combine signals from the first and second half-wave rectifier circuits to determine an average of the currents flowing through the two light-emitting sections, and 
 
 the control section operates based on an output from the stabilization circuit. 
 
     
     
       5. A light source device comprising:
 the light source inverter of  claim 1 ; and 
 a plurality of light-emitting cathode fluorescent lamps driven by the light source inverter to emit light. 
 
     
     
       6. The light source device of  claim 5 , further comprising:
 a light guide plate directing the light emitted from the plurality of light-emitting cathode fluorescent lamps in a predetermined direction. 
 
     
     
       7. A display device comprising:
 the light source device of  claim 6 ; and 
 a display section achieving display by receiving light from the light source device. 
 
     
     
       8. A liquid crystal display panel comprising:
 the light source device of  claim 6  serving as a backlight; and 
 a liquid crystal panel achieving display by receiving, from behind, light from the light source device, varying orientation of liquid crystal and thus changing a light transmittance of liquid crystal. 
 
     
     
       9. A display device comprising:
 the light source device of  claim 5 ; and 
 a display section achieving display by receiving light from the light source device. 
 
     
     
       10. A liquid crystal display panel comprising:
 the light source device of  claim 5  serving as a backlight; and 
 a liquid crystal panel achieving display by receiving, from behind, light from the light source device, varying orientation of liquid crystal and thus changing a light transmittance of liquid crystal. 
 
     
     
       11. The light source inverter of  claim 1 ,
 wherein the light-emitting sections are arranged in a line, and the current detection section detects currents flowing through two of the light-emitting sections arranged at both ends of the line. 
 
     
     
       12. The light source inverter of  claim 1 ,
 wherein the light-emitting cathode fluorescent lamps included in the light-emitting sections are connected in series, 
 the power supply sections include two transformers each including a coil provided at a secondary side of each respective one of the two transformers, 
 one of the coils of the two transformers is connected to one end of the light-emitting cathode fluorescent lamps connected in series, and 
 the other of the coils of the two transformers is connected to the other end of the light-emitting cathode fluorescent lamps connected in series.